Generally, a data storage device is a computing device that reads data from and writes data onto storage media. A data storage device may contain moving parts or may not have any significant moving parts. An example of a data storage device with moving parts is a traditional disk drive where a disk (e.g., a spinning platter) rotates and has one or more heads that read and write data. There are different types of disk drives for different types of disks. For example, a hard disk drive (HDD) reads and writes hard disks, and a floppy drive (FDD) accesses floppy disks. A magnetic disk drive reads and writes magnetic disks, and an optical drive reads and writes optical disks. A data storage device without any significant moving parts is generally referred to as a solid-state drive. An example of a solid-state drive is a Flash drive.
Data storage devices are utilized in an increasing number of applications. Home computers, business servers, laptops, and many other electronic devices, such as routers, digital cameras, cell phones, and the like, use data storage devices. Certain applications require a high level of security for the data stored and transferred in the data storage device. These applications include banking applications, commercial applications, medical applications, criminal justice applications, military applications, radar systems, sonar systems, data recorders, tactical computers, fire-control systems, airborne reconnaissance systems, network systems, and the like.
Data security is an important concern for data storage devices used in these secure applications. For example, many operating systems and file systems do not actually erase data from a hard disk when deleting a file; instead, a directory or inode entry is merely deleted from a table. The actual data in the file remains on the hard disk until over-written. Even when data from a storage location has been deleted, the physical properties of the storage medium, such as magnetic hysteresis, can often allow the deleted data to be discovered.
In an attempt to allay some of these concerns, some solid-state drives offer a secure erase feature in which data is deleted and overwritten in each storage location multiple times (e.g., six times). The effectiveness of such a solution relies on the secure erase operation having enough time to complete before being interrupted and on the storage locations being in a re-writable condition. One component of many solid-state drives is storage space arranged in a number of Flash storage blocks. A typical aspect of such Flash storage blocks, or simply “Flash blocks,” is that after significant usage they will often reach a certain state in which the data in the Flash block cannot be erased or re-written. It is still possible in this state, however, to read data from the Flash block, which poses a data security risk to the device.
Although typical solid-state drives routinely employ wear-leveling write algorithms to evenly distribute write operations across all the storage locations of the device, some Flash blocks will eventually wear out and can no longer be erased or re-written by a secure erase feature. Additionally, if data is not able to be erased for any reason from a solid-state drive, then that data remains readily available to any user who comes into possession of the solid-state drive. Accordingly, there is a need for improving data security of data storage devices.